import time

def test1():
    while True:
        print('——1——')
        yield

def test2():
    while True:
        print('——2——')
        yield
def main():
    t1= test1()
    t2= test2()
    while True:
        next(t1)
        next(t2)

        
if __name__ == '__main__':
    main()
